The present invention relates to nonvolatile erasable programmable memories and more specifically, techniques for organizing or laying out the memory cells on the integrated circuit.
Memory and storage is one of the key technology areas that is enabling the growth in the information age. With the rapid growth in the Internet, World Wide Web (WWW), wireless phones, personal digital assistants (PDAs), digital cameras, digital camcorders, digital music players, computers, networks, and more, there is continually a need for better memory and storage technology. A particular type of memory is nonvolatile memory. A nonvolatile memory retains its memory or stored state even when power is removed. Some types of nonvolatile erasable programmable memories include as Flash, EEPROM, EPROM, MRAM, FRAM, ferroelectric, and magnetic memories. Some nonvolatile storage products include CompactFlash (CF) cards, MultiMedia cards (MMC), Flash PC cards (e.g., ATA Flash cards), SmartMedia cards, and memory sticks.
A widely used type of semiconductor memory storage cell is the Flash memory cell or floating gate memory cell. There are other types of memory cell technologies such as those mentioned above. Flash and floating gate memory cells are discussed as merely an example. The discussion in this application would also apply to other memory technologies other than Flash and floating gate technology with the appropriate modifications. The memory cells are configured or programmed to a desired configured state. In particular, electric charge is placed on or removed from the floating gate of a Flash memory cell to put the cell into two or more stored states. One state is a programmed state and another state is an erased state. A Flash memory cell can be used to represent at least two binary states, a 0 or a 1. A Flash memory cell can also store more than two binary states, such as a 00, 01, 10, or 11; this cell can store multiple states and may be referred to as a multistate memory cell, a multilevel, or multibit memory cell. This allows the manufacture of higher density memories without increasing the number of memory cells since each memory cell can represent more than a single bit. The cell may have more than one programmed state. For example, for a memory cell capable of representing two bits, there will be four programmed states.
Despite the success of nonvolatile memories, there also continues to be a need to improve the technology. It is desirable to improve the density, speed, durability, and reliability of these memories. It is also desirable to reduce power consumption and reduce the cost per bit of storage.
As can be appreciated, there is a need for improving the performance and reducing the power consumption of nonvolatile memories. In particular, by arranging and laying out the memory cells of an integrated circuit so bitlines of the memory cells are segmented, this will reduce noise between bitlines and improve the performance and reliability, and reduce power consumption.